Don't do it! Healthy hair has a pH of 4.5 to 5.5 lemon juice has a pH of 2.0 - 2.5. This mean that lemon juice is about 1000 times more acidic than your hair. If you choose to do this you need to water it down. Unless you're hair is naturally light (level 7 or lighter) it will only turn orange (not a good look for anyone). If you have artificial highlights (with bleach) the lemon juice could cause the hair to break. I'm not saying it will just that it could.

If you want to lighten your hair but yet still keep the "natural" look have a friend give you a soap cap. It's equal parts of shampoo, low volume developer, and a powder lightener. Work it from the ends to the scalp. It shouldn't be on the head any longer than 10 minutes. I hope this helps

So, I'm a (16) yr old guy with short dirty blonde hair, I took 1/2 cup of room temperature water mixed with 1 1/2 Tbsp. of pure bottled lemon juice and 2 1/2 Tbsp. of olive oil and mixed it into a bowl and damped my hair and basically just lathered it into my hair. Let it sit for 30 minues to 1 hour, depending on how light you want your hair.

And just saying, it came out fantastic, to a great light caramel color, I didn't think it would work so I tried it. The reason I added olive oil was because I found that lemon juice really dried out my hair and made it unhealthy looking and feeling, and the olive oil really moisturizes your hair and helps sustain the color. Once you sit there for 30 minutes to an hour just rinse with water. I did this in the pm, so in the am I just took a shower using deep conditioner shampoo and my hair looks great and feels great! This is a highly recommended remedy for you!